This invention broadly relates to a composition and process for the electrodeposition of copper, and more particularly, to a composition and method for the electrodeposition of copper from aqueous acidic copper plating baths, especially from copper sulfate and fluoroborate baths. More specifically, the invention relates to the use of a novel brightening agent, preferably in conjunction with supplemental brightening agents to produce bright, ductile, level copper deposits with good recess brightness on metal substrates over a wide range of bath concentrations and operating current densities.
A variety of compositions and methods have heretofore been used or proposed for use incorporating various additive agents for electrodepositing bright, level, ductile copper deposits from aqueous acidic copper electroplating baths. Typical of such prior art processes and compositions are those described in U.S. Pat. Nos. 3,267,010; 3,328,273; 3,770,598 and 4,110,176 which are assigned to the same assignee as the present invention. According to the teachings of U.S. Pat. No. 3,267,010, it has been found that bright, level and ductile deposits of copper can be produced from an aqueous acidic copper electroplating bath incorporating therein a bath-soluble polymer of 1,3-dioxolane, preferably in conjunction with supplemental brightening agents including organic sulfide compounds; U.S. Pat. No. 3,328,273 teaches the use of a bath-soluble polyether compound containing at least 6 carbon atoms as a brightening agent, preferably in conjunction with aliphatic polysulfide compounds; U.S. Pat. No. 3,770,598 teaches the use of a bath-soluble reaction product of polyethyleneimine and an alkylating agent to produce a quaternary nitrogen as a brightener, preferably in conjunction with aliphatic polysulfides, organic sulfides and/or polyether compounds; while U.S. Pat. No. 4,110,176 teaches the use of a bath-soluble poly (alkanol quaternary ammonium salt) as a brightening agent such as produced from the reaction of a polyalkylenimine with an alkylene oxide.
While the compositions and methods described in the aforementioned United States patents provide for excellent bright, ductile, and level copper deposits, the bath composition and process of the present invention provide for still further improvements in many instances in the ductility, leveling and brightness of the copper deposit particularly in recess areas.